I see your point, but I deeply hope you're wrong. Don't take me wrong, would love to see the scene, but it's just too far off, I think it would lose the thing that makes this game extra special. It would become essentially what every other game here is, a "catch 'em all". Also, I think we're closer to a point where we might have the option to break Maya & Josy throuple and pick one of them, than to the point were we add someone in.
Josy would definitely do Sage or Jill and accept them in the relationship.
Maya, I'm not so sure. Maybe a one time thing with Sage, but I doubt it.
Sage I think would be open to one time thing with any of them, but I don't see her wanting and even accepting it as a relationship.
Jill is discovering sex at 21 and also is a prude. The only threesome I see with her is with Bianca and in very specific situation (that involves a lot of alcohol and is followed by a lot of regret)